1. Field of the Invention
The present invention relates to a twisted nematic (TN)-mode liquid crystal display (LCD) apparatus capable of improving gray scale display characteristics.
2. Description of the Related Art
In a prior art TN-mode LCD apparatus, twisted-mode type liquid crystal is inserted between two plane electrodes. In the prior art LCD apparatus, when the twisted angle of liquid-crystal molecules in the liquid crystal is larger than a value around 270xe2x80x2, the tilt angle of liquid crystal molecules has an S shaped relationship to the voltage applied between the electrodes. Therefore, the transient orientation state of liquid crystal molecules during a rising voltage is different from that during a falling voltage. As a result, when an intermediate voltage between a high voltage and a low voltage is applied between the electrodes there are two orientation states of liquid crystal molecules mixed within one pixel. Thus, a large hysteresis is generated in the voltage-to-light transmittance characteristics, so that a gray scale display is impossible.
It is an object of the present invention to provide a TN-mode LCD apparatus capable of improving gray scale display characteristics even when the twisted angle of liquid crystal molecules is large.
According to the present invention, in a liquid crystal display apparatus including two electrodes and a twisted-mode type liquid crystal layer inserted between the electrodes, an electric field in the liquid crystal layer between the first and second electrodes is changed within one pixel, when a voltage is applied between the electrodes.
Also, in a liquid crystal display apparatus including two electrodes, two oriented layers formed on inner surfaces of the electrodes, respectively, and a twisted-mode type liquid crystal layer inserted between the oriented layers, one of the electrodes has an uneven surface, so that pretilt angles of liquid crystal molecules in the liquid crystal layer are fluctuated within one pixel.
Further, in a liquid crystal display apparatus including two plane electrodes, two oriented layers formed on inner surfaces of the electrodes, respectively, and a twisted-mode type liquid crystal layer inserted between the oriented layers, one of the oriented layers is divided into a plurality of domains each receiving rubbing processes of different directions, so that pretilt angles of liquid crystal molecules in the liquid crystal layer are fluctuated within one pixel.
In addition, in a liquid crystal display apparatus including two plane electrodes, two oriented layers formed on inner surfaces of the electrodes, respectively, and a twisted-mode type liquid crystal layer inserted between the oriented layers, the liquid crystal layer includes a polymer network generated by polymerization of monomer, so that pretilt angles of liquid crystal molecules in the liquid crystal layer are fluctuated within one pixel.